Spectroscopic Analysis of Molybdenum Model Compounds by: 1.Infrared 2. 1 H NMR 3.Electronic (UV/vis) 4.ESI-MS Why? What did I make? How do molecules differ?

UV/vis Spectroscopy = Electronic Spectroscopy What does it monitor / probe? What information about molecule can one obtain? What if 350 nm has  = 8,000 M -1 cm -1 and 550 nm has  = 80 M -1 cm -1 ?

IR Spectroscopy What does it tell us? What more information about molecule can one obtain? Mo O O O O O

1 H NMR: what do you expect to see?

a b c a b c Expected: 3 resonances, 2 -CH 3 (a & c with 6H) and 1 H (b) ( B-H not visible due to broadening) … plus H’s on cation TEA = [N(CH 2 CH 3 ) 4 ]+

[Tp*Mo(S)(S 4 )] — 1 H NMR: what do you expect to see?

a a a e e b b b d d Mo=S Mo=O TEA + -CH 2 - TEA + -CH 3 c c c f f

a b c d e f a b c a b c d ef Mo=S Mo=O TEA + -CH 2 - TEA + -CH 3

R1 ≠ R2: How many H’s expected in NMR from pyrazole rings? All -methyl and ring H’s will be unique: see 6 -Me and 3 ring H

How many H’s expected in NMR from detc liagnds?

Mass Spectometry Facility Dr. Arpad Somogyi

Electrospray Ionization Mass Spectrometry ESI-MS black box mass detector magnetic field separates light and heavy mass ions Molecules in gas phase as ions + or -

Electron impact ionization

Electrospray ionization method makes tiny droplets Vacuum removes solvent Electric potential creates + and - ions

All Mo molecules are identified by a characteristic series of lines: Mo isotopes: 92 Mo, 94 Mo, 95 Mo, 96 Mo, 97 Mo, 98 Mo,

YELLOW (calculated mass spectrum) MassRelative abundance

RED (calculated mass spectrum) MassRelative abundance

BLUE (calculated mass spectrum) MassRelative abundance

PURPLE (calculated mass spectrum) MassRelative abundance

Y B P R All have one Mo atom More lines, more Mo atoms

RED mass spectrum 409.6

YELLOW mass spectrum 444.6

BLUE full mass spectrum

YELLOW (high mass species)

Accurate mass : for Modetc3 MassRelative abundance Accurate mass : for MoOdetc3 MassRelative abundance

MoOdetc 2 : Mo1S4O1N2C10H20mass: g/mol MoOdetc 2. NCCH 3 : Mo1S4O1N3C12H23mass: g/mol MoOCl 2 detc 2 : MoCl2S4O1N2C10H20mass: g/mol Mo 2 O 3 detc 4 : Mo2S8O3N4C20H40mass: g/mol MoOS 2 detc 2 : MoS6ON2C10H20mass: g/mol

MoOCl 2 detc 2 : MoCl2S4O1N2C10H20 Accurate mass : MassRelative abundance

MoOdetc 2 : Mo1S4O1N2C10H20 Accurate mass : MassRelative abundance

Mo 2 O 3 detc 4 : Mo2S8O3N4C20H40 Accurate mass : MassRelative abundance

MoOS 2 detc 2 : MoS6ON2C10H20 Accurate mass : MassRelative abundance